Better understanding of how environmental and biological risk factors influence adolescent problem behavior - a constellation of co-morbid precocious or deviant behaviors, including delinquency, substance use, and high risk sexual behavior - is critical for ameliorating individual mental health and relieving society of the enormous cost imposed by these behaviors. One potential environmental protective factor is religiosity, defined as affiliation with a religious tradition and involvement in organized religious activities, Epidemiological research indicates that religiosity is associated with reduced problem behavior, including less alcohol and substance use, less delinquent behavior, later initiation of sexual intercourse, and fewer sexual partners. Classical and modern sociological theories posit that religiosity decreases deviant behavior by instilling beliefs about divine sanctions, encouraging prosocial ties that foster empathy and concern for collective well-being, facilitating the intergenerational communication of conforming values, and buffering against psychological distress that otherwise may be acted out in problem behavior. Because adolescents are not involved in religious organizations at random, however, genetic and environmental third variables may influence both religiosity and problem behavior, thus confounding observed associations. For example, two-parent homes are more likely to be religious than single-parent homes, and the presence of both biological parents is associated with less delinquency. Thus, family structure confounds associations between religiosity and delinquency. Furthermore, the effects of religiosity on problem behavior may interact with adolescents' genetic liabilities. The proposed project uses behavior genetic methodology and data from the National Longitudinal Study of Adolescent Health to elucidate the processes underlying associations between religiosity and adolescent problem behavior. Specifically, the project will test whether twin and sibling pairs discordant for religiosity also differ in their levels of problem behavior, an association that controls for genetic and environmental influences shared by siblings. This "quasi-experimental" design provides a more rigorous test of whether religiosity is actually a protective factor against problem behavior. In addition, the project will combine distinct threads of inquiry into a comprehensive model of the effects of genes and religiosity on problem behavior that simultaneously considers genotype-environment correlation and interaction. The project is distinctive in its integration of sociological, psychological, and biological perspectives on adolescent problem behavior, and will inform prevention and intervention strategies designed to ameliorate this critical mental health issue. [unreadable] [unreadable] [unreadable]